Spark plug



Sept. 22, 1936. J. McKoNE 2,055,204

SPARK PLUG Filed Feb. e, 1935 Patented Sept. 22, 1936 SPARK PLUG n Leo J. McKone, Cleveland, Ollio, asisignor to Leo Corporation, Chicago, Ill.,

Illinois 4 a corporation of Application February 6, 1935, Serial No. 5,192

2 Claims.

This invention relates to spark plugs and more particularly to plugs useful with the present day types of aluminum or aluminum alloy heads employed on internal combustion engines, especially engines oi automotive vehicles. The term aluminum as herein used, is used generically, and not by way of limitation, and is used to designate all aluminum alloys which are capable of use in the manufacture of heads for internal combustion engines.

Since the advent of aluminum heads, or heads of other than iron, for internal combustion engines, diiiiculties have been encountered in the use of spark plugs having steel or iron spark plug body shells.

Among such difliculties may be mentioned the damage resulting from the use of spark plugs, having steel shells, in aluminum heads of internal combustion engines. Due to the great difference in expansion of the two metals, it has been found impossible to remove such spark plugs from an aluminum head when the engine, so equipped, becomes heated to its most efficient operating temperature, without damage to the threads of the spark plug holes of the head. Resistance to removal of the plugs, under such circumstances, is caused by the more rapid cooling of the aluminum head, thus contracting about the steel plugs, as the high residual heat present in the steel shells of the plugs prevents as rapid contraction of the shells. Spark plugs having steel or brass shells, have been broken by twisting Vin efforts to remove them from aluminum heads.

I have -found that spark plug shells made of non-ferrous alloy, such as aluminum bronze, of special content, have overcome the above recited objections. lThe alloy is substantially the same as that used for' the manufacture of the aluminum heads, so that the rates of expansion and contraction of the heads and shells are substantially the same. Furthermore, such shells prevent the formation of carbon deposit, as they do not have the residual heat retaining characteristics of steel shells.

While brass, in any form, is cheaper than the non-ferrous alloy of the present invention, it cannot be successfully used for spark plug shells because of presence of zinc, which causes disintegration of the brass shells when subjected to the frequent temperature changes incidental to internal combustion engine operation. Furthermore, the alloy of the present invention possesses much greater tensile strength than brass, which feature is important, because of the limitations as to thickness and other dimensions in manufacture of spark plug shells.

Many attempts have been made toprevent undue heating of the porcelain cores of spark plugs, to prevent pre-ignition or knocking, and also to increase the life and efficiency of the cores.

(Cl. 12S-.169)

I have found that the cores may be kept below excessively high temperatures, due to combustion, by designing the spark plugs so that the noses .of the cores lie within the ilame swept 4zone of the shells. Further, by making the shell taperV close to the core nose, the temperature of the core is maintained at a proper fpoint. Theu'se" of the non-ferrous alloy of the present invention causes rapid heat transfer, so that the part of the shell within the combustion zone of the engine is not so hot as to stratify the gases. A lso,'the use of axially extending cooling ns on the shells and the elimination of the hex nut part o f the shell aids in keeping down the shell temperature.

#With spark plugs constructed 'in accordance with the present invention, I have successfully eliminated tknocking from engines having compression ratios as high as 8 to 1.

Combustion knock is occasioned, mainly, by hot spark plug shells. The gaseous mixture entering through the inlet port is rapidly swirled in the cylinders. This swirling is known as turbulence'. The greater `the turbulence, the greater number of times the mixture passes over the hot plugs, thereby creating the Vso-called "hot poker effect, YThis causes formation of stratiied layers of slow and fast burning mixtures inthe vicinity of the plugs. The rapid burning layers ignite rst and strike theslow burning layers, thereby causing a rapid increase of pressure and consequent knock i By keeping the portionsfof the plugs that l.project into the combustion chambers, at'engine head temperatures, stratication ofthe gaseous mixture is prevented and a homogeneous, evenly expanded gas charge is available at vthe `time of ignition. l

Spark p lugsof the present invention may 'be placed in Aan engine over the intake valves, w`hich is recognized as the best for maximum power in L head engines. By placing the plugs over the exhaust valves, the compression ratio 4may be increased and the same power output achieved, as where the plugs are over the inlet valves. The plugs may also, advantageously, be placed between the inlet and outlet valves, similar to the practice in I head engines.

Spark plug shellsr made `of the non-ferrous alloy of the present invention removes the hot poker. eiect ofthe parts of the shells projecting Vinto the cylinders, as any residual heat is convected directly to the atmosphere.

Another advantage derived from the present invention is'that a desirable temperature is maintained at the electrodes which heat quickly, when starting the cool'or cold engine, which vprevents free carbon formation, caused Vvby rich mixtures employed for-warming a col'djengine.` A high residual temperature in the. plus Shells ,is eliminated Iby the shell construction'of this invention,

2 by reason of the high conductivity of the nonferrous shell and the convection of heat to the atmosphere by the axially extending ribs or iins, thereby attaining a successful heat equilibrium.

The use of shrouds aboutv the ribbed shells causes even cooling of the shells, especiallyin engines where some of the plugs are exposed to; fan draft, open hood louvers and the like. 'VIheshrouds may be removed when engines are usedv in warm climates. K

An object of the present invention is to improve spark plug construction for internal combustion engines having aluminum or aluminum alloy heads.

Another object of the present invention is to provide spark plugs having shells of non-ferrous composition. ,A further object of the present invention is to provide spark plug construction whereby the spark gap is maintained constant. v

A furtherobject of the present invention is to provide a spark plug construction whereby heat access, to the core is reduced.

A still further object of the present invention is toprovide a spark plug shell having heat radij ating means.Y

Another and yet further object of the present invention is to provide a spark plug bush having heat radiating means.

The invention has for an additional object the provision of a spark plug shell and bush each provided with heat radiating means, which means are also capable of engagement by suitable tools for installing or removing the plugs, and also for assembling and dis-assembling the shells and bushes.

` views thereof are as follows;

Figure 1Y is an elevational view of a spark plug constructed in accordance with the principles of thepresent invention, shown as applied to an internal combustion engine, the head being fragmentally shown and in section.

Figure 2 is an enlarged View, of a spark plug constructed in accordance with the principles of the present invention, showing the bush and core in elevation, and the shell in section.

Figure 3 is a 'top plan view of the spark plug illustrated in Figures 1 and 2, and *Y Figure 4 is a fragmental bottom view of lthe plug. f

The drawing will now be explained.

The illustrated form of spark plug includes a shell A, a porcelain core B, and a bush or bushing C. Y

kThe shell A is provided with an enlarged interior I for receiving the core B and having a portion of its length threaded to receive the bushneck 2 is` tapered, as at 6 for a purpose to be later explained, while the lower Yextremity of the neck is substantially cylindrical, as at 'L The neck is formed with an extension 8 which is bored at 9 perpendicularlyto the axis of the shell, for receiv-` 2,o55,2o4 a ing an electrode ID. The electrode I is in the form of a straight wire and has its free end extending beyond the axis of the shell. The shell A has formed on it a plurality of axially extending outwardly projecting fins or ribs II for heat dissipation. The lower extremities of these fins or lribs are inclined inwardly as at I2, to enable ready application of the spark plug to an engine head having a pocket or recess I3 provided for the plug.

The core B is cylindrical for a major portion of its length, and is tapered convergently at its firing end, as -at I4, the taper of the end I4 being substantially that of the taper 6 of the neck of the shell. `'Ihe tapers of the portion 6 of the neck and the portion I4 of the core are such that any axial line drawn on either would be parallel to a corresponding line on the other. The core B is provided with the usual electrode I5 having one extremity as at I6 projecting from the ring end of the core for co-operating with electrode Ill to provide a spark gap. The other end of the ,electrode I5 is provided with the usual means for connection thereto of a conductor. The core B is provided, intermedate its length, with an annular enlargement II, the diameter of which is slightly less than the diameter ofthe bored portion of the shell A.

The bushing C is fashioned in the form of a cylindrical collar, iitted on its exterior to engage with the threads on the interior of the bore on the shell A, and at its lower extremity is provided with an inclined foot I8 for a purpose to be later explained.

The upper or outer end of the bushing C is provided with a plurality of axially extending lugs I9 which are angularly spaced about the perimeter of the bushing, which lugs serve the dual purpose of heat radiating fins and also as means engageable by suitable tools in connecting the bushing C to the shell or in removing the bushing from the shell.

When the parts of the spark plug of the present invention are assembled, a gasket 20 is rst inserted in the bore of the shell A and comes to rest against an inclined shoulder 2l fashioned in the shell. The core is next inserted, the lower portion of the enlargement I1 resting against the gasket 20. The gasket 20 serves to center the core in the shell and also serves to determine the position of the extremity of the active point I6 of the core electrode. Next a gasket is app-lied about the core and comes to rest against the upper portion of the enlargement I'I of the core. Next the bushing is threaded into the bore of the shell A with the inclined margin I8 thereof against the gasket, to secure the core and parts in assembled and operative relation. The bushing C is tightened so that there is no likelihood of the parts becoming loose or separated.

Figure 2 illustrates the position of the several parts when the plug is assembled in the manner described.

It will be observed that the plug construction is such that but a small space exists between the taper 5 of the neck 2 of the shell and the tapered end I4 of the core and that the extremity of the end I 4 of the core is inwardly of the lower extremity of the neck. This serves to reduce the amount of heat reaching the core, due to combustion, and thus prolongs the life of the spark plug, especially the core.

In applying a spark plug of the present invention to an engine head 5, a suitable gasket 22 is applied about the neck prior to its insertion in the spark plug hole 4 of the head. The lower extremities of the fins or ribs II form, as at 23, shoulder means for abutment against the gasket 22 to tighten it in place, as the plug is tightened in the hole 4. The ribs or ns II serve as means for engagement by a suitable tool useful in applying the plug to an engine head or in removing it from the head.

The ribs or iins II are made preferably thin, so as to readily dissipate heat and thus maintain the plug in a comparatively cool condition.

The shell A and the bushing C are made of nonferrous alloy, preferably one having copper as its major constituent, to thereby readily conduct heat away from the core B.

The non-ferrous alloy preferably employed for the manufacture of the plug of the present invention is one having substantially the same cefcient of expansion as that employed in the manufacture of the engine head 5.

A composition comprising approximately eight parts of copper to one part of aluminum has been found to be very satisfactory in use. Such composition produces what is herein termed an aluminum bronze.

Specifically, a composition of 88% copper and 12% aluminum has proved most satisfactory in manufacturing the plugs of the present invention. A non-ferrous alloy of the character specified very readily conducts heat away from the core B of such plug, thereby prolonging the life of the plug, and at the same time the expansion of such alloy is comparable with that of the expansion of the aluminum head 5, so there is, for all practical purposes, no expansion differential due to heat of combustion.

The novel electrode construction of the present invention contemplates the positioning of the point I6 of the core electrode to terminate substantially even with the extremity of the neck 2 of the shell, while the other electrode I0 projects from an extension 8 of the shell neck, in a direction perpendicular to the shell axis, with its free end extending beyond the electrode I6 of the core. The electrode I0 is straight throughout its length so that as this electrode becomes. eroded from use, there is still maintained the same spark gap between the electrodes I0 and I6.

Any suitable way may be followed for securing the electrode I 0 in position. It has been found satisfactory to secure the electrode I0 in the bore and retain it therein by means of pins 24 driven into suitable apertures in the extremity of the extension 8 axially thereof, to engage the electrode iii and prevent its ready displacement from the extension, or, in lieu of the pins, indentations may be made by a suitable tool.

It will be observed that the spark plug of the present invention is so constructed as to readily dissipate heat created in internal combustion engines by reason of combustion of the mixture. The provision of the non-ferrous shell and bushing enables ready heat dissipation, which dissipation is accelerated by the p-rovision of the ribs or fins II on the shell and the lugs I9 on the bush- Y ing, and the hex nut, usual in steel shells, has been eliminated.

If desired, a shroud D may be applied about the ribs or fins II. 'I'he fins I I are notched at 25 to receive the inturned upper margin of the shroud and thus position the shroud on the shell. The

shroud D may be removed, if desired, by slipping it out of the notches 25.

Said shroud D is an open ended cylinder of thin sheet metal, such as aluminum or other metal having a high rate of heat conductivity. The use of the shroud provides a chimney-like effect for the convection of air past the fins. The shroud D purposely does not extend to the upper ends of the iins I I but leaves the upper n ends exposed to permit engagement of said iin ends by a twelve point wrench or similar tool. As shown in Figure 3, there are preferably twelve ns so as to` facilitate the use of a twelve point wrench.

'I'he manufacture of the shells and bushings of the same, or substantially the same, coecient of expansion as is employed for the manufacture of the head 5 of the engine, eliminates any expansion differential due to the presence of heat and thus prolongs the life of the spark plugs and heads.

The novel electrode construction of the present invention enables longer use of such plugs without having to remove them for examination of the spark gaps.

A spark plug constructed in accordance with the principles of the present invention is cool, and inasmuch as it contains no residual heat, stratification of the mixture adjacent the plug, and considerable knock are eliminated, thereby tending for ecient operation of the internal combustion engines with which such plugs may be used.

The plugs of the present invention warm up quickly but do not at any time become too hot, as the heat is readily dissipated to the atmosphere.

One of the important advantages of the type of plug herein disclosed is that the shell lends itself readily to a die casting operation.V Either a twopiece or single piece permanent mold may be used. Since no subsequent machining operation is required, the manufacture of my plug is relatively inexpensive.

The invention has been described herein more or less precisely as to details, yet it is to be understood that the invention is not to be limited thereby, as changes may be made in the arrangement and proportional parts, and equivalents may be substituted, without departing from the spirit and scope of the invention.

The invention is claimed as follows:

1. A spark plug comprising an elongated cylindrical shell having a reduced lower end portion to enter a bore in the head of an engine, and a tapered lower portion merging into a straight enlarged portion which is provided with peripherally spaced and longitudinally extending outstanding ribs which dene unobstructed air passages open at their lower ends and merging with the surface of said lower portion.

2. A spark plug comprising an elongated cylindrical shell of aluminum bronze, said shell having a reduced lower end portion to enter a bore in the head of an engine, and an elongated body portion which is provided with peripherally spaced and longitudinally extending outstanding and integral fins defining unobstructed vertical air passages which have entrance and exit openings in vertical alignment with the longitudinal axis of said passages.

LEO J. MCKONE. 

